An example of an indexable cutting insert for milling, mentioned at the beginning, is disclosed in PTL 1 below.
The cutting insert in PTL 1 is generally polygonal, e.g., square, and has a straight minor cutting edge (minor edge) formed at each corner of the polygon so as to extend in a direction perpendicular to the bisector of the corner in plan view.
In other cases, instead of the straight minor cutting edge, a circular minor cutting edge having a large radius of curvature and approximating to a straight line is provided at each corner of the polygon.